A narcotic analgesic and antitussive. It is metabolized in the liver by ethylmorphine-N-demethylase and used as an indicator of liver function. It is not marketed in the US but is approved for use in various countries around the world. In the US it is a schedule II drug (single-entity) and schedule III drug (in combination products).

This compound belongs to the class of organic compounds known as morphinans. These are polycyclic compounds with a four-ring skeleton with three condensed six-member rings forming a partially hydrogenated phenanthrene moiety, one of which is aromatic while the two others are alicyclic.

Ethylmorphine is metabolized by the enzyme cytochrome P450 2D6 to morphine. Morphine is a narcotic pain management agent indicated for the relief of pain in patients who require opioid analgesics for more than a few days. Morphine interacts predominantly with the opioid mu-receptor. These mu-binding sites are discretely distributed in the human brain, with high densities in the posterior amygdala, hypothalamus, thalamus, nucleus caudatus, putamen, and certain cortical areas. They are also found on the terminal axons of primary afferents within laminae I and II (substantia gelatinosa) of the spinal cord and in the spinal nucleus of the trigeminal nerve. In clinical settings, morphine exerts its principal pharmacological effect on the central nervous system and gastrointestinal tract. Its primary actions of therapeutic value are analgesia and sedation. Morphine appears to increase the patient's tolerance for pain and to decrease discomfort, although the presence of the pain itself may still be recognized. In addition to analgesia, alterations in mood, euphoria and dysphoria, and drowsiness commonly occur. Opioids also produce respiratory depression by direct action on brain stem respiratory centers.

Mechanism of action

Ethylmorphine is metabolized by the liver enzyme cytochrome P450 2D6 to morphine. The precise mechanism of the analgesic action of morphine is unknown. However, specific CNS opiate receptors have been identified and likely play a role in the expression of analgesic effects. Morphine first acts on the mu-opioid receptors. The mechanism of respiratory depression involves a reduction in the responsiveness of the brain stem respiratory centers to increases in carbon dioxide tension and to electrical stimulation.
It has been shown that morphine binds to and inhibits GABA inhibitory interneurons. These interneurons normally inhibit the descending pain inhibition pathway. So, without the inhibitory signals, pain modulation can proceed downstream.

Absorption

Not Available

Volume of distribution

Not Available

Protein binding

Not Available

Metabolism

After ingestion, ethylmorphine is converted to morphine in the human liver by the CYP450-isozyme CYP2D6, similarly to codeine.